In recent years, to archive low-power consumption of a laser printer or a copy machine, improvement in performance for fixing at low temperature (low temperature fixing properties) is demanded for toner for electro photography.
In order to raise low temperature fixing properties, a polyester-based resin is generally used as binder resin in toner, and further improvement in low temperature fixing properties is designed by reducing the softening point of the resin.
However, when improvement in the low temperature fixing properties of electro-photographic toner is designed by lowering the softening point of binder resin, a hot offset resistance will decline significantly.
Therefore, the method to include a wax in electro-photographic toner is generally used.
However, generally, the compatibility between a wax and polyester-based binder resin is extremely poor, so a wax cannot be included in binder resin, for example, only about 2 to 3% of the weight.
Even if it can include a wax about 2 to 3% of the weight in binder resin, the wax dispersion in toner will not be uniform, and the hot offset will be occurred.
Thus, to obtain the electro-photographic toner that was superior in low temperature fixing properties and in a hot offset resistance was difficult.
As a method to improve the dispersibility of a wax, it is attempted to raise the compatibility between a wax and polyester-based binder resin; and for example, manufacturing electro-photographic toner by using the composition containing binder resin and a wax with a compatibilizer that further makes compatible for these is known.
As such a composition, in the concrete, for example, a composition, which contains binder resin of polyester-based resin, a wax, and the compatibilizer obtained by reacting maleic anhydride denaturation polyolefin with polyester resin, is disclosed (for example, see patent documents 1.).
This compatibilizer has a formation adding polyolefin that is superior in compatibility with a wax to a similar-based polyester resin of a binder resin.
The compatibility between the wax and the polyester-based resin as binder resin improves by using this compatibilizer, and the wax can be used about 5% of the weight to the weight of binder resin, which is much more than former.
However, about 5% of the weight is insufficient for the content of a wax to the weight of binder resin in order to obtain the toner that is superior in a hot offset resistance, and it may be necessary to be about 10% of the weight.
In the patent documents 1, the polyester resin used for preparing the compatibilizer is about 0.02-1 mmol/g in hydroxyl group (about 1-70 mg KOH/g as in hydroxyl value,) and it is a polyester resin generally used in the field of the electro-photographic toner. However, in such polyester resin, little quantity of the hydroxyl group exists for binding of polyolefin.
For this reason, polyolefin for sufficient quantity cannot be applied, which the content of a wax to be used about 10% of the weight to the weight of binder resin.
Even if it tried to increase the amount of the compatibilizer used and to increase in the quantity of the wax which can be dispersed in binder resin, since the molecular weight of the polyolefin chain added to the compatibilizer is as large as 1000-20000, the compatibility between the compatibilizer and the binder resin does not be satisfactory. Thus, to mix with binder resin in large quantities is difficult.
Patent documents 1: Japanese Unexamined Patent Application, First Publication No 2005-316378